docs: def block(self, group=False, custom=False):
          '''
          获取板块数据
  
          :param group:
          :param custom:
          :return: pd.dataFrame or None
          '''
          reader = BlockReader()
          symbol = os.path.join(self.tdxdir, 'block_zs.dat')
  
          if symbol is not None:
              return reader.get_df(symbol, group)
  
          return None